Pore filled metal wear surfaces and method of pore filling the same



Sept. 18, 1962 w. c. AR LD ETAL 3,054,649

FORE FILLED METAL w SURFACES AND METHOD OF PORE FILLING THE SAME Filed Oct. 5, 1961 FIG.3

lREGION B FIG.I

INVENTORS WALTER CL ARNOLD EDWARD F.TINDER BY ATTO RN EY United States Patent Ofifice 7 3,54,649 Patented Sept. 18, 1962 3,054,649 PORE FILLED IVETAL WEAR SURFACES AND ME'IHGD {)F PGRE FILLING TIE SAME Walter C. Arnold and Edward F. Tinder, Beloit, Wis.,

assignors to Fairbanks, Morse & Co., Yonkers, N.Y.,

a corporation of Illinois Filed Oct. 3, 1961, Ser. No. 142,711 14 Claims. (Cl. 309-2) This invention relates to metal wear surfaces such as the bore surfaces of engine cylinders and the like, and to a method of improving such surfaces. While not limited thereto, the present invention concerns more particularly engine cylinders or cylinder liners having Wear surfaces of chromium.

In the internal combustion engine art, it is well known to provide on the bore surface of a cast iron cylinder or liner, as by plating thereon, a metal such as chromium characterized by frictional wear resistance markedly greater than that of cast iron. Such chromium plating in the cylinder bore affords a working surface having a high degree of wear resistance to the piston and piston rings in frictional travel thereover. The chromium surface, moreover, is of a porous character having irregular recesses, as channels and pits or voids, which receive and retain lubricating oil. Such pores or irregular recesses thus give to the chromium surface the ability to wet or hold a film of oil. However, it is found in practice that the oil in such pores escapes, in large degree, the oil scraping action of the usual piston oil scraper rings. Consequently, in each power stroke of the piston, oil in the pores exposed to the combustion space thus is left behind to burn in the cylinder. The result is an undesirable and usually inordinate consumption of cylinder lubricating oil.

It is found that a fair degree of lubricating oil con sumption control can be obtained with chromium of a soft or minimum hardness character, but the wear resistance of such chromium plating is not much better than that of cast iron. On the other hand, it is most desirable for engine cylinders or liners to employ as the wear surface thereof, chromium or hard or high wear resistance character. Commercial chromium plating tcehniques, however, have failed to provide cylinder wear surfaces of hard chromium afi'ording high wear resistance, and yet at the same time having a porosity pattern yielding good piston ring control of lubricating oil consumption.

Accordingly, the prime purpose of the present invention is to so improve the surface presented by the chromium plating in a cylinder or liner, as to permit the use of hard chromium for high wear resistance, while affording a wear surface permitting a degree of lubricating oil consumption control highly desirable in engine operation.

Pursuant to the foregoing purpose, one object of the invention is to provide a chromium plated cylinder or liner wherein the pores or irregular recesses of the chrmium plating thereof are filled with an organic material securely bonded therein and characterized by oil wettability, lubricity, and the ability to withstand the temperature and pressure conditions obtaining in the engine cylinder combustion space during engine operation.

Another object is to provide a method or process of filling the pores or irregular recesses in a chromium wear surface, with an organic material having the characteristics referred to in the foregoing object.

Other objects and advantages of the present invention will appear from the following description thereof, and the accompanying drawings, wherein:

FIGS. 1 and 2 are enlarged sectional views showing the character of the cylinder chromium surface during different stages of pore filling in accordance with the present invention; and

FIG. 3 shows an actual photograph presenting a greatly enlarged view (substantially to 1 magnification) of a representative portion of a cylinder interior that has been treated by the process of the present invention.

In accordance with the present invention, an engine cylinder or liner having a plated bore surface of hard chromium affording a Wear surface of high wear resistance, is treated in a manner and by the method hereinafter described, to attain a filled condition of the portion of the chromium plate. More particularly, the pore filled condition is provided at least over the chromium plate area traversed by the usual piston oil control ring or rings, and the material filling the pores is of predetermined character as hereinafter described, whereby to permit and assure the attainment of a desirable high degree of cylinder lubricating oil control by the piston oil control rings, as well as to afford other advantages hereinafter appearing.

Chromium surface pore filling with tin and other metals has not proved successful, this for a number of reasons including the difficulty of effective filing and bonding. Accordingly, the present invention contemplates a nonmetallic, or organic, filling material of highly comminuted or finely divided character, presenting very small size particles determined as not in excess of three (3) microns, to assure pore penetration and substantially complete filling of the chromium surface pores. The filling material further must be capable of firm bonding to the pore surfaces as by a suitable thermosettable resin, and must possess the important characteristics of surface wettability by lubricating oil, inherent lubricity (low coefiicient of friction), and full capability of withstanding maximum temperature and pressure conditions of the order obtaining in the cylinder combustion space of high compression or diesel engines during engine operation.

It is found that the material most suitable to substantially complete pore filling and having the necessary characteristics above noted, is a phenolic modified tetrafluoroethylene known in the trade as Emralon 310, being a commercial product of the Acheson Colloids Co., Port Huron, Michigan. This material is provided in liquid mixture form for ready application to the chromium surface, as by bonding or spraying thereon. The prime constituents of the mixture are pigment and binder, the pigment being tetrafluoroethylene in particle form and having the size of the particles no larger than three (3) microns and averaging less than one (1) micron, and the binder being a phenolic resin of thermosettable character. Formation of the liquid mixture is attained by adding 22 parts by weight of tetrafluoroethylene resin in a water emulsion, to 100 parts by weight of phenolic resin in a suitable solvent carrier as for example, a ketone solvent. Mixing must be conducted slowly and with sufficient agitation, to assure complete dispersion of the tetrafluoroethylene particles throughout the mixture.

In general according to the present invention, the desired pore filled condition of the chromium wear surface is obtained by forming a coating of the filling mixture on the previously-cleaned surface to be treated, the coating being of a final thickness to assure filling of the pores or irregular recesses in the treated surface, thence curing the coating, and finally removing the coating portion above the treated surface, leaving the pores or irregular recesses filled with the cured material to a condition flush with the exposed chromium surface. FIG. 1 illustrates in fragmentary enlarged section, a cast iron cylinder portion 9 having the chromium layer 10 plated thereon, and the coating 11 on the chromium layer and filling the pores 12 thereof. FIG. 2 is a similar fragmentary enlarged section, showing the stage of removing the coating portion 14 above the chromium surface, as by a sharp tool or the like indicated at 15, thereby leaving coating material completely filling the pores, as at 16 and 18, with each pore filling having the exposed surface 19 thereof flush with the exposed surface 20 of the chromium layer 10. The resultant pore filled condition of the chromium wear surface in a representative cylinder liner portion is shown by FIG. 3 which is a photograph, more particularly a photomicrograph of substantially one hundred to one magnification, providing a view of the liner bore surface portion. In this view, the surface of the cast iron cylinder liner is shown in region A, While the surface of the chromium plating on the liner is shown in region B. The irregular shaped areas in region B are the filled pores or recesses of the chromium layer.

Referring now to the method of obtaining the pore filled condition as provided by the present invention, the following is a specific example of the method, but the given example should not be taken as limiting the invention to the details thereof.

According to the present example, an engine cylinder liner is provided having its inner bore surface plated with chromium of high wear resistance character, the chromium layer having pores or irregular recesses therein opening to the exposed surface of the layer. The liner is treated to clean the chromium surface and prepare the irregular recesses therein for the filling material. Initially in such treatment, the liner is completely immersed in an alkali bath for a period not less than about minutes and at a bath temperature not less than about 180 F. The bath suitable for the purpose, is a solution containing sodium hydroxide, trisodium phosphate, sodium carbonate and water.

Following the alkali bath treatment, the liner is given a first Wash by immersion for a period not less than about one minute, in water at a temperature not less than about 160 F., and then a second wash by immersion for a period not less than about two minutes in warm water at a temperature not more than about 90 -F. After washing, the liner is given an electroetchant treatment by immersion in a bath of chromic acid solution at a temperature of not more than about 90 F. In this treatment, the liner is the anode in an electrical circuit including a lead cathode in the liner bore, the circuit being energized from a suitable direct-current power source having a minimum voltageof 12 volts and a current capacity up to about 500 amperes. Circuit energization is maintained at about 400 amperes for a period not less than two minutes nor more than three minutes, resulting in a slight etch of the liner chromium plating and hence positive cleaning of the pores or irregular recesses thereof.

With completion of the electroetchant step, the liner is immersed in Water at a temperature not less than 200 F., for a period not less than two minutes, and then is thoroughly dried. Drying to remove all moisture from the liner bore surface may be accomplished rapidly by air blasting using filtered air at suitable pressure, preferably not less than about 75 pounds per square inch (p.s.i.). Upon drying, the liner bore surface is given final preparation for coating, by spraying preferably with methanol, then removing all traces of the methanol as by air blast drying with filtered air at a pressure of 75 psi. or more.

The chromium Wear surface of the liner is now ready for coating to fill the pores thereof. Advantageously, the tetrafluoroethylene mixture in liquid form as before noted, is applied by spraying as by a conventional pressure spray gun employed in paint spraying and the like. The spraying operation is conducted in stages in order to build up a coating of suflicient thickness to assure complete filling of substantially all pores or irregular recesses in the chromium plating. To that end, the chromium surface is sprayed over the whole or such portion thereof selected for pore filling, at a rate to leave a relatively thin wet film thereon, as of the order of 0.0002 inch in thickness. Whereupon the applied film is allowed to air dry for a period not less than about five minutes. That procedure then is repeated for the second film and each succeeding film to the extent of between 10 and 20 film layers for producing a final dry coating varying correspondingly between about 0.002 and 0.003 inch in thickness. Dry coating in the given thickness range has been found to be entirely adequate to the obtaining of complete filling of substantially all pores in the coated area of commercial chromium plating such as is provided in engine cylinder liners and the like. The number of film layers within the range stated, to be applied to the chromi um plating of a given cylinder liner, may .be readily determined from inspection of the chromium surface thereof. Where inspection of the area to be coated reveals relatively large area and perceptibly deep pores, then 18 to 20 film layers normally will assure complete pore filling. On the other hand, where on inspection the pores appear to be uniformly quite shallow in depth, 10 to 12 film layers normally should be adequate.

Upon completion of the coating process, the liner is allowed to air dry for about two hours or more, and then placed in a suitable baking oven for curing the phenolic binder in the coating mixture. To properly cure the hinder, the liner is brought to a temperature within the range of 300 F. to 310 F. and then retained (at such temperature) in the oven for a period of between 60 and 75 minutes. At the end of the baking period, the liner is removed from the oven and allowed to air cool. Whereupon the coating on the chromium surface is removed as by a sharp scraping tool, to expose the chromium surface and to leave the chromium pores completely filled with the coating material to a level flush with the exposed chromium surface. It is to be pointed out here that as a result of the baking step, the resulting cured phenolic binder firmly bonds the tetrafiuoroethylene particles together as Well as firmly bonds the filling material to the surfaces of the chromium .plate pores or recesses.

In accordance with the now described method, the porous chromimum wear surface of a cylinder liner may be thus conditioned 'to have the pores or irregular recesses therein filled with the indicated Emralon 310 material, which thereby affords the several advantages hereinbefore stated. It will be apparent now that the invention is applicable to articles other than engine cylinders or liners, having wear surfaces of chromium or the like and where similar advantages are to be obtained by filling the pores of such wear surfaces. Also, it is to be recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. An engine cylinder provided with a piston ringengaging wear surface having a multiplicity of irregular recesses therein, and material filling said recesses, said material comprising finely divided non-metallic particles characterized by oil-wettability and a low coelficient of friction, having the particles bonded together and bonded to the surfaces of the recesses by a thermosetting resin binder. 2. An engine cylinder as defined by claim 1, in which the said finely divided non-metallic particles are further characterized by an average particle size less than one micron. v

3. An engine cylinder provided with a piston ring-engaging wear surface having a multiplicity of irregular recesses therein, and material filling said recesses substantially flush with the wear surface, said material comprising finely divided non-metallic particles characterized by oil-,wettability, lubricity and an average particle size less than one micron, having the particles bonded together and bonded to the surfaces of the recesses by a thermosettting resin binder.

4. An engine cylinder as defined by claim 3, in which the said non-metallic particles are particles of tetrafluoroethylene.

5. An engine cylinder comprising a base metal and a chromium layer thereon, the chromium layer providing a piston ring-engaging Wear surface and having a multiplicity of irregular recesses therein, and material filling said recesses, said material comprising finely divided nonmetallic particles characterized by oil-wettability and lubricity, having the particles bonded together and bonded to the surfaces of the recesses by a thermosetting resin binder.

6. An engine cylinder comprising a base metal and a chromium layer thereon, the chromium layer providing a piston ring-engaging wear surface and having a multi plicity of irregular recesses therein, and material filling said recesses substantially flush with the Wear surface, said material comprising finely divided non-metallic particles characterized by oil-wettability, lubricity and average particle size less than one micron, having the particles bonded together and bonded to the surfaces of the recesses by a thermosetting resin binder.

7. An engine cylinder as defined by claim 6, in which the said non-metallic particles are particles of tetrafiuoroethylene.

8. An article of manufacture providing a metal wear surface having irregular recesses therein, and material filling said recesses substantially flush with the Wear surface, said material comprising non-metallic solid particles characterized by a low coefficient of friction and average particle size less than one micron, having the particles bonded together and bonded to the surfaces of the recesses by a thermosetting resin binder.

9. An article of manufacture providing a chromium Wear surface having irregular recesses therein, and material filling said recesses substantially flush with the Wear surface, said material comprising non-metallic solid particles characterized by oil wettability, lubricity and average particle size less than one micron, having the particles bonded together and bonded to the surfaces of the recesses by a thermosetting resin binder.

10. An article of manufacture providing a chromium wear surface having irregular recesses therein, and material filling said recesses flush with the Wear surface, said material comprising finely divided particles of tetrafiuoroethylene having an average particle size of less than one micron, having the particles bonded together and bonded to the surfaces of the recesses by a thermosetting resin binder.

11. The method of treating an engine cylinder providing a piston ring-engaging Wear surface having irregular recesses therein, to aflford improved piston ring control of lubricating fluid on the wear surface, comprising the steps of cleaning the wear surface and recesses therein, depositing on the wear surface a liquid coating mixture including finely divided non-metallic particles of lubricant fiuid-Wettable character and an uncured thermosettable resin bonding agent, to form a coating thereon and filling said recesses, baking the coating to cure the resin bonding agent and thereby bond the particles together and to the wear surface and the surfaces of the recesses therein, and removing the coating in extent sufficient to expose both the Wear surface and the coating material filling the recesses.

12. The method of treating an engine cylinder provid ing a piston ring-engaging chromium wear surface having irregular recesses therein, to afford improved piston ring control of lubricating fluid on the wear surface, comprising the steps of cleaning the Wear surface and recesses therein, depositing on the wear surface and in the recesses thereof a liquid coating mixture including finely divided nonmetallic particles characterized by lubricant fluid wettability, lubricity and average particle size less than one micron, and an uncured thermosettable resin bonding agent, baking the coating to cure the resin binding agent and thereby bond the particles together and to the wear surface and the surfaces of the recesses therein, and removing the coating in extent sufficient to expose both the wear surface and the coating material filling the recesses.

13. The method as defined by claim 12, in which the said finely divided non-metallic particles are particles of tetra-fluoroethylene.

14. The method of treating an engine cylinder providing a piston ring-engaging chromium wear surface having irregular recesses therein, to afford improved piston ring control of oil lubricant on the wear surface, comprising the steps of immersing the cylinder in an alkali bath, washing the cylinder by immersion in Water, immersing the cylinder in an electroetchant chromic acid bath, wash ing the cylinder by immersion in Water, drying the cylinder, spraying the cylinder Wear surface with methanol, drying the cylinder Wear surface, depositing on the wear surface and in the recesses thereof a liquid coating mixture consisting essentially of finely divided tetrafiuoroethylene particles and an uncured thermosettable resin binding agent, drying the coated cylinder Wear surface, baking the coating to cure the binding agent and thereby bond the coating to the Wear surface and surfaces of the recesses, and thence removing the coating in extent sufiicient to expose both the Wear surface and the coating material filling the recesses.

References Cited in the file of this patent UNITED STATES PATENTS 2,846,943 Belk Aug, 12, 1958 FOREIGN PATENTS 563,863 Canada Sept. 30, 1958 

1. AN ENGINE CYLINDER PROVIDED WITH A PISTON RINGENGAGING WEAR SURFACE HAVING A MULTIPLICITY OF IRREGULAR RECESSES THEREIN, AND MATERIAL FILLING SAID RECESSES, SAID MATERIAL COMPRISING FINELY DIVIDED NON-METALLIC PARTICLES CHARACTERIZED BY OIL-WETTABILITY AND A LOW COEFFICIENT OF 